The present invention relates generally to electrical actuator subassemblies, and more particularly to such subassemblies used in fuel injectors.
Many electronically-controlled fuel injectors use electrical actuators mounted on the outside of the injector body to control the initiation and termination of injection events. A common means of attaching the electrical actuator to the injector body is with three or more bolts, positioned beyond the periphery of the actuator""s armature, which penetrate through the actuator and the injector body itself. As a result, the diameter of the injector body must be great enough to accommodate not only the armature, but also the bolts. The use of bolts not only creates a minimum diameter for the injector body, but the space taken up by the bolt holes creates limitations on the possible positioning of hydraulic lines and other components within the injector body. In addition to the benefits of conserving radial space, it is often necessary to position the injector underneath the engine valve cover, making conservation of vertical space desirable. Thus, in most examples of these fuel injectors, the electrical connector comes out of the side of the assembly rather than the top.
A threaded cap allows a lesser injector body diameter by obviating the need for bolts outside the periphery of the armature. One example of a design using a threaded cap and a top-mounted electrical connector can be found in U.S. Pat. No. 5,961,052, issued to Coldren et al. on Oct. 5, 1999. In the Coldren version, a cap with internal threads is mated directly to external threads on the injector body itself. This design has proven successful, however, the need to rotate the cap to tighten the assembly against the injector body would make the positioning of the electrical connector on the side of the injector difficult if not impossible.
The present invention is directed to solving one or more of the problems set forth above.
In one aspect, an electrical actuator subassembly is provided which has a metallic body with a set of external threads. Either a piezoelectric actuator or a solenoid coil is mounted in the metallic body.
In another aspect, a fuel injector is provided which includes an injector body, a collar with a set of internal threads attached to the injector body, and an electrical actuator subassembly including a metallic body with a set of external threads. In one embodiment, a piezoelectric actuator is mounted in the metallic body, whereas in a second embodiment a solenoid coil is used. The electrical actuator subassembly is mounted on the injector body by mating the subassembly""s external threads with the collar""s internal threads.
In still another aspect, a method of attaching an electrical actuator to a body component is provided. The method includes the steps of attaching a collar having a set of internal threads to a body component and providing an electrical actuator subassembly that includes a metallic body with a set of external threads. The method further includes mounting either a piezoelectric actuator or a solenoid coil in the metallic body and mating the external threads of the electrical actuator subassembly to the internal threads of the collar.